Conventionally, electrical power tools having vibration control mechanisms have been proposed. For example, Japanese Patent Application Publication No. 2005-040880 discloses an electrical power tool including a casing that has a handle, a motor casing, and a gear casing connected with one another. An electrical motor is accommodated in the motor housing. A motion conversion mechanism that converts a rotation motion of the electrical motor into a reciprocation motion is provided in the gear casing. A cylinder extending a direction perpendicular to the rotation axis of the electrical motor is provided in the gear casing. A tool support portion is provided on the front side of the cylinder and is capable of attaching or detaching a working tool.
A piston is provided in the cylinder and is slidably provided along the inner periphery of the cylinder. The piston reciprocates along the inner periphery of the cylinder by the motion conversion mechanism. A striking member is provided in the front section of the cylinder and is slidably provided along the inner periphery of the cylinder. An air chamber is formed in the cylinder between the piston and the striking member. An intermediate member is provided in the front side of the striking member and is slidably provided back-and-forth within the cylinder. The working tool mentioned above is positioned at the front side of the intermediate member.
The rotational driving force of the electrical motor is transmitted to the motion conversion mechanism, and the motion conversion mechanism moves the piston in the cylinder in the reciprocation motion. The reciprocation motion of the piston repeatedly increases and decreases the pressure of the air in the air chamber, thereby applying an impact force to the striking member. The striking member moves forward and collides with the rear end of the intermediate member, thereby applying the impact force to the working tool. The workpiece is fractured by the impact force applied to the working tool.